1. Field of the Invention
The present invention relates to a tapered needle plug for a bleed port on a float operated pneumatic valve assembly for a pneumatic operated liquid level switch for tanks and vessels.
2. Description of the Related Art
There are a number of existing devices that include float operated valves. In each case, when the liquid level rises or falls in a tank or vessel, a float shifts a pneumatic valve to one of two positions. Some existing devices couple the float to the pneumatic valve using a magnet couple while others use mechanical linkage.
Some existing devices control the pneumatic valve by a pad or flap. Large forces are required to seal such a pad or flap, requiring the use of a powerful magnet where magnet coupling is used.
Based on the foregoing, it is desirable to provide a float operated pneumatic valve utilizing a tapered needle plug instead of a pad or flap. This would reduce the force needed to seal the port, which in turn makes the pneumatic valve more reliable and allows for lower operating specific gravities. It also means the coupling used to connect the float to the valve does not have to supply as much force, which makes for more coupling options, such as a weaker magnetic coupling.
Some existing pneumatic conical or tapered valves with a magnetic switch are direct acting, such as seen in Felgote (U.S. Pat. No. 2,893,427). It is desirable to provide a magnetic opposing pole snap switch with a block and bleed valve arrangement.
It would also be desirable to provide a tapered needle plug for a bleed port on a float operated pneumatic valve assembly wherein a block and bleed valve is externally adjustable.